1. Field of the Invention
The present invention relates to an object observation apparatus and, more particularly, to an apparatus and method of observing the integrated circuit pattern of a semiconductor wafer or the like using, e.g., an electron beam.
2. Related Background Art
With higher integration degrees of recent LSIs, the defect detection sensitivity required for samples such as a wafer and mask is increasing. For example, to detect defective portions on a wafer pattern 0.25 μm in DRAM pattern size, a detection sensitivity of 0.1 μm is required. In addition, demands have arisen for inspection apparatuses which satisfy both an increase in detection sensitivity and an increase in detection speed. To meet these requirements, surface inspection apparatuses using an electron beam have been developed.
A known example of an apparatus for scanning an electron beam on an object and observing secondary electrons from the object is a scanning electron microscope (SEM). A known example of an inspection apparatus for inspecting defects using an electrooptic system as a primary optical system is one disclosed in Japanese Patent Laid-Open No. 7-181297 (corresponding to U.S. Pat. No. 5,498,874). As disclosed in Japanese Patent Laid-Open No. 7-249393 (corresponding to U.S. Pat. No. 5,576,833), a pattern inspection apparatus is known which forms the sectional shape of a beam into a rectangular or elliptic shape through a rectangular cathode and quadrupole lens.